Huawei H12-831_V1.0 Exam - Topic 3 Question 75 Discussion

Comprehensive and Detailed In-Depth

1. Understanding the MPLS Data Flow in the Figure

PC1 (1.1.1.1) sends a ping to PC2 (3.3.3.3).

The MPLS domain includes R1, R2, and R3.

R1 pushes an MPLS label onto the packet (Label: 300).

Packets from PC1 to PC2 are label-switched (MPLS forwarding).

Packets from PC2 to PC1 do not carry an MPLS label (IP forwarding).

2. Evaluating Each Answer Option

Option A: 'If the device is R3, R3 forwards the packet from PC1 to PC2 over an IP route.'

Incorrect.

The packet carries an MPLS label (Label 300) when entering the MPLS domain.

This means that R3 forwards the packet using MPLS, not a standard IP route.

If R3 were using an IP route, there would be no MPLS label in the packet.

Option B: 'Packets from PC1 to PC2 are forwarded based on MPLS labels in the MPLS domain.'

Correct.

The packet capture shows an MPLS label (Label 300), proving that PC1's traffic is being forwarded using MPLS switching inside the MPLS domain.

This confirms that MPLS is being used for forwarding in one direction (PC1 PC2).

Option C: 'Packets from PC2 to PC1 are forwarded based on the IP packet header in the MPLS domain.'

Correct in concept but incorrect in context.

The packet capture shows that the return traffic (PC2 PC1) does not have an MPLS label.

However, the phrase 'in the MPLS domain' makes this statement misleading, as R3 is forwarding based on pure IP routing, not MPLS forwarding.

Option D: 'PC1 pings PC2.'

Correct.

The packet capture clearly shows ICMP Echo Request (ping) from PC1 (1.1.1.1) to PC2 (3.3.3.3) and an ICMP Echo Reply from PC2.

This confirms that PC1 is pinging PC2 successfully.

Final Answer:

B and D are correct.

HCIP-Datacom-Advanced Routing & Switching Technology Reference:

MPLS Label Forwarding and Static LSPs

MPLS vs. IP Routing in Different Traffic Flows

Packet Header Analysis in MPLS Networks